Components of certain equipment, such as that used in the petroleum and petrochemical industry, which includes the exploration, production, refining, manufacture, supply, transport, formulation or blending of petroleum, petrochemicals, or the direct compounds thereof, are often monitored to maintain reliable operation. However, such components can involve harsh conditions, such as high temperature, high pressure, and/or a corrosive environment, making it difficult or costly to obtain reliable measurements.
Measurement of the level of, or interfaces between, one or more media in a vessel, such as a desalter unit or subsea production well petrochemical applications, can provide for enhanced control and operation. For example, a desalting operation can be facilitated and enhanced by determining the location of interfaces between gas, foam, oil, emulsion, water and/or solids in a refinery desalter unit. Better emulsion band detection and profiling can improve level, mix valve, and chemical injection control and can allow partial automation of the desalter operation. Likewise, in connection with subsea separation of gas, water, oil, emulsion, and sand from a well, measurement of the interface or levels between the various media can provide enhanced control of the extraction process.
Conventional approaches to measure liquid level/interface can include monitoring locations of floated displacers, capacitance, wave reflectance, or energy absorption. However, these conventional approaches can suffer from certain drawbacks. For example, float-type level measurement is based on liquid density difference (such as between oil and water), and therefore it can be difficult to deploy multiple displacers for multiple level/interface monitoring. Furthermore, the moving displacers can become coated by liquid (such as crude oil), resulting in sensor failure. Capacitance probes require direct contact with fluids to measure electrical properties and therefore, may deliver false readings if fouling or waxing occurs on the probe. Additionally, because the electrical properties can be temperature dependent, capacitance-based probe techniques can also require temperature compensation. Wave reflectance approaches can have limited penetration depth because certain materials can absorb the acoustic, radio frequency, or microwaves, and thus are unsuitable for multi-level/interface monitoring. Moreover, use of energy absorption techniques can be limited to narrow temperature ranges depending upon the sensitivity of the equipment involved.
As stable desalter emulsions are becoming increasingly common due to the increase in penetration of challenged crudes in refineries, crudes with high asphaltenes, high TAN, high solids, low API gravity, or high viscosity tend to form emulsions that are difficult to break. As a result, water and salt removal can be reduced, the oil content of the brine can increase, and disruptions in operation can become more common. Improved emulsion band detection and profiling in a desalter unit therefore would improve level, mix valve, and chemical injection control and allow for partial automation. In like manner, improved detection of interfaces between mixture components in subsea separation operations can improve control over extraction.
Accordingly, there is a continued need for improved techniques for identifying levels or interfaces of media in a vessel.